JPH05124522A - Torque detecting device for motor-driven type power steering - Google Patents

Abstract

PURPOSE:To permit the exceedingly simple assembly by reducing the number of parts and obtaining the constitution of a movable iron core and an input shaft in relatively simple manner with high precision. CONSTITUTION:A torque detecting device consists of an output shaft 2, input shaft 1 having an inclined groove 1b formed at one edge in the axial direction, movable iron core 4 having a projection part 4b which is projectingly installed on the inner peripheral surface, and a coil part 5 having a circular inner wall on which the movable iron core 4 slide. The input shaft 1 and the output shaft 2 are connected through a torsion bar 3, and the movable iron core 4 is engaged in rotatable manner together with the output shaft 2 and in slidable manner in the axial direction, and the movable iron core 4 is installed by insertion- engaging the projection part 4b in the inclined groove 1b of the input shaft 1 so as to be coaxial to the input shaft 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque detecting device for an electric power steering, which has a small number of parts and is extremely easy to assemble.

[0002]

2. Description of the Related Art In recent years, electric power steering has been widely used, and a torque detecting portion thereof has a substantially cylindrical movable iron core through which an input shaft is inserted and a circumferential inner wall arranged around the movable iron core. A differential transformer consisting of a coil section having a coil, and an input shaft provided with a handle and an output shaft transmitted to the steering device in the vicinity of a connecting portion so as to be coaxial with the pinion shaft. A movable iron core is provided.

Specifically, as shown in FIGS. 9 and 10, a spiral inclined hole is formed through a cylindrical side surface of the movable iron core c, and the inclined hole is formed in an input shaft such as a pinion shaft. A guide protrusion is formed on the movable iron core c and a guide groove is formed on the output shaft so that the engagement pin p fixed by press fitting is inserted, and the output shaft is slidable in the axial direction. It becomes a mechanism and responds to the rotation difference due to the elastic twist of the torsion bar that serves to connect the input shaft and the output shaft.
The movable core c moves on the input shaft within a predetermined range to generate a voltage in the coil portion d, and the electric motor operates to assist in steering.

[0004]

By the way, in the manufacture of the conventional torque detecting portion, as shown in FIG. 10, in the cam-shaped mechanism including the engaging pin p and the inclined hole, the engaging pin p
When press-fitting into the mounting hole of the input shaft, there is a possibility that defects such as tilting of the engagement pin p due to press-fitting of the engagement pin p and disengagement due to incomplete press-fitting may occur in the manufacturing process.

Further, the insertion of the slanted hole slidable in the axial direction and the engagement pin p requires high precision, and it must be formed without play, and the high precision machining enables the manufacture. Not only is it difficult, but the manufacturing cost is high, and there is the problem of becoming a high-priced product.

[0006]

Therefore, as a result of earnest studies to solve the above problems, the inventor
An output shaft, an input shaft having an inclined groove formed at one end in the axial direction, a movable iron core having a protrusion on its inner peripheral surface, and a coil portion having a circumferential inner wall on which the movable iron core slides. While connecting the input shaft and output shaft with a torsion bar,
The movable core is locked so as to be rotatable with the output shaft and slidable in the axial direction, and the protrusion is inserted and engaged with the inclined groove of the input shaft so that the movable core is coaxial with the input shaft. By providing the torque detection device for electric power steering provided, the number of parts can be reduced, the assembly can be extremely simplified, and the production efficiency can be improved, and the above-mentioned problems are solved.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

Reference numeral A denotes a torque detecting portion of the electric power steering apparatus, in which the input shaft 1 and the output shaft 2 are connected by a torsion bar 3 and, as shown in FIG. A cylindrical movable iron core 4 is provided so as to be concentric with the input shaft 1 and the output shaft 2.

As shown in FIG. 1B, the input shaft 1 is provided with a handle H, and is connected to the output shaft 2 via a joint by a steering device S. As shown in FIG. 2, the input shaft 1 and the output shaft 2 are connected by a torsion bar 3, and the rotation of the input shaft 1 transmits the rotation to the output shaft 2 via the torsion bar 3. It is a thing.

The torsion bar 3 connecting the input shaft 1 and the output shaft 2 causes a difference in rotation angle between the output shaft 2 and the input shaft 1 due to a reaction force received by the tire from the road surface. At that time, the torsion bar 3 is twisted.

At the connecting portion between the input shaft 1 and the output shaft 2, as shown in FIGS. 2 and 3B, first, the input shaft 1 is connected.
An engaged portion 1a is formed at one axial end of the output shaft 2, and an engaging portion 2a is further formed at one axial end of the output shaft 2. The engaged portion 1a and the engaging portion 2a have an appropriate gap. And is configured to be engageable.

The engaged portion 1a of the input shaft 1 and the engaging portion 2a of the output shaft 2 are, as shown in FIG. 6, specifically, a flat plate having two parallel flat surfaces of a predetermined width. The engaged portion 1a of the input shaft 1 is formed as a projection, and the engaged portion 1a of the input shaft 1 is formed as a concave cutout portion into which the flat plate-like protruding body can be loosely inserted. In the inserted state, it is normally in a non-contact state and has a predetermined interval.

When the output shaft 2 rotates via the torsion bar 3 due to the rotation of the input shaft 1, if the torsion of the torsion bar 3 is within a predetermined range, the engaging portion 2a and the engaged portion 1a are separated from each other. The rotation is transmitted from the input shaft 1 to the output shaft 2 without contact.

The movable iron core 4 serves as a core of an operating transformer, and a coil portion 5 having a circumferential inner wall exists around the movable iron core 4, and the movable iron core 4 has its coil. It is configured to slide on the inner circumference of the portion 5, and the sliding causes the electric motor M to operate, and an assisting action occurs when the handle is operated.

On the movable iron core 4, as shown in FIG.
There is provided a locked portion 4a which is formed by cutting out into a concave shape capable of locking with the engaging portion 2a of the output shaft 2. As shown in FIG. 4, the locked portion 4a is engaged. The movable core 4 is slidable along the protruding direction of the portion 2a.

Further, as shown in FIGS. 5 and 6, an inclined groove 1b formed in a spiral shape is formed on the outer peripheral surface of one end of the input shaft 1 in the axial direction, and the inner peripheral surface of the movable iron core 4 is further formed. Is provided with a protrusion 4b, the protrusion 4b is inserted into an inclined groove 1b formed in the input shaft 1, and the input shaft 1 rotates about an axis to move the movable iron core 4 The inner protrusion 4b slides in the axial direction of the input shaft 1 along the inclined groove 1b.

As shown in FIGS. 2 to 6 and the like, the movable iron core 4 is integrally formed with protrusions 4b and the like formed on the inner peripheral surface thereof. Often formed as bond gold.

The movable iron core 4 is, as shown in FIG.
In order to always maintain a fixed position with respect to the input shaft 1, a stopper 7 fixed to the input shaft 1 via an elastic body 6 such as a coil spring is fixed so that the predetermined position can be maintained.

Further, a worm gear 8 is fixed to the electric motor M and a wheel gear 9 is fixed to the output shaft 2, and the rotational force of the electric motor M is transmitted to the output shaft 2 via the worm gear 8 and the wheel gear 9.

A movable iron core 4, a coil portion 5 and the like are mounted in a casing 10 at a connecting portion between the input shaft 1 and the output shaft 2.

The electric motor M has a structure in which a large amount of current flows when the movable iron core 4 slides inside the coil portion 5 and the position is displaced.
It is located at the axial center of the.

FIG. 8 shows another embodiment of the present invention, which is a pinion type, in which a worm gear 8 is formed on the output shaft 2 and meshes with the rack teeth of the rack shaft.

[0023]

According to the present invention, the output shaft 2, the input shaft 1 having the inclined groove 1b formed at one end in the axial direction, the movable iron core 4 provided with the protrusion 4b on the inner peripheral surface thereof, and the movable iron core 4 are provided. And a coil portion 5 having a circumferential inner wall 5a that slides. The input shaft 1 and the output shaft 2 are connected by a torsion bar 3, and the movable iron core 4 is rotatable with the output shaft 2 and For electric power steering in which the movable iron core 4 is provided so as to be slidable in the direction, insert the projection 4b into the inclined groove 1b of the input shaft 1 and become coaxial with the input shaft 1. First of all, by using the torque detection device,
In addition, the number of parts can be reduced, the structure of the movable iron core 4 and the input shaft 1 can be realized relatively easily and with high accuracy, and secondly, the assembly can be simplified.

These effects will be described in detail. Since the protrusion 4b is formed in the movable iron core 4, the protrusion 4b is formed.
Can be configured by simply inserting the input shaft 1 into the movable iron core 4 while inserting it into the inclined groove 1b of the input shaft 1.

That is, since the movable iron core 4 is previously formed with the protrusion 4b which is slidable along the axial direction of the input shaft 1, in order to control the torque of the electric motor as in the conventional type. It is not necessary to press-fit a pin made of a different material to the iron core and forcefully attach it like the torque detection part of.

Further, in the conventional type, the pin requires extremely precise dimensional tolerance in the guide groove for sliding the iron core on the input shaft side, and thus requires advanced manufacturing technology. It was necessary to satisfy both of the dimensional tolerances with high precision at the same time as the press-fitting work. However, in the present invention, since the protrusion 4b is integrally formed on the inner peripheral surface of the movable iron core 4, the protrusion 4b is formed. And the inclined groove 1b of the input shaft 1 can be manufactured by paying attention only to the accuracy of only the dimensional tolerance, which improves the production efficiency.
Since the number of parts can be reduced and the production cost can be reduced, there is an advantage that it can be provided at a low price.

Next, the movable iron core 4 is previously provided with the protrusion 4
Since b is formed, there is no need to press a pin between the movable iron core 4 and the input shaft 1 with a press, a hammer or the like as in the conventional case, so that a defective product due to deformation etc. at the time of manufacturing is not generated. It can be prevented.

[Brief description of drawings]

FIG. 1A is a side view with a partial cross section showing an embodiment of the structure of the present invention, and FIG. 1B is a schematic view of an electric power steering using the present invention.

FIG. 2 is a sectional view of an essential part of the present invention.

3 (a) and 3 (b) are longitudinal sectional front views of a main part of the present invention.

FIG. 4 is a side view of a main part of the present invention.

FIG. 5 is a plan view of an essential part of the present invention.

FIG. 6 is an exploded perspective view of a main part of the present invention.

FIG. 7 is a schematic view showing an assembly work state of the present invention.

FIG. 8 is a vertical sectional side view of another embodiment of the present invention.

FIG. 9 is an enlarged view of a main part showing a conventional technique.

10 is a cross-sectional view taken along the line XX of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Input shaft 1b ... Inclined groove 2 ... Output shaft 3 ... Torsion bar 4 ... Movable iron core 4b ... Projection part 5 ... Coil part 5a ... Circumferential inner wall

Claims (1)

[Claims] 1. A coil unit having an output shaft, an input shaft having an inclined groove formed at one axial end thereof, a movable core having a projection on an inner peripheral surface thereof, and a circumferential inner wall on which the movable core slides. The input shaft and the output shaft are connected by a torsion bar, and the movable iron core is locked so as to be rotatable with the output shaft and slidable in the axial direction, and the projection is inclined groove of the input shaft. A torque detecting device for an electric power steering, wherein the movable iron core is provided so as to be inserted into and engaged with the input shaft so as to be coaxial with the input shaft.